1. Field of the Invention
This invention relates to air conditioners and methods of controlling the same. More particularly, the invention relates to techniques concerning an air conditioner, which can provide a gentle cooling mode for gently cooling a room while the temperature thereof is held in the neighborhood of a predetermined temperature, and a gentle drying mode for drying air in the room while substantially maintaining the present temperature of the room, in addition to a cooling mode and a heating mode.
2. Description of the Prior Art
Air conditioners are roughly classified into a separate type in which an interior unit and an exterior unit are separated from each other, and an integral type in which the two units are accommodated in the same housing. In either type, a freezing cycle circuit of heat pump type is provided, in which a compressor, a four-way valve, an integral heat exchanger, a pressure reducer (or an expansion valve) and an internal heat exchanger are successively provided on a main duct line in the mentioned order.
The freezing cycle circuit is used in a heating mode and also a cooling mode by switching its four-way valve. The internal heat exchanger, however, is recently in a trend of increasing a size for improving its heat exchange capacity and reducing the power consumption. The internal heat exchanger also has a coolant heat exchanger with a plurality of branches for increasing the heat exchange efficiency in the cooling operation and also in the heating operation.
Correspondingly, the air conditioner can be set in a plurality of operating modes such as a "strong cooling" mode, an "intermediate cooling" mode, a "weak cooling" mode and a "drying" mode (or commonly termed substantial weak cooling mode).
In the drying mode, intermittent operation of the internal unit fan or like control is provided. Such a measure, however, has a problem that it cannot permit sufficient drying. Another well-known method for drying uses an expansion valve, which is provided on the coolant flow line in the internal heat exchanger and permits drying by re-heating. In this case, however, the coolant flow line cannot be branched. Therefore, the heat exchange efficiency in the cooing and heating operations is inferior to the case where the coolant flow line is branched.
Accordingly, a construction as shown in FIG. 16 is proposed in Japanese Laid-Open Patent Publication No. 8-105646. In this construction, an internal heat exchanger 4 is provided in an internal unit housing 1 such that it faces air suction holes 2 formed in the front wall of the housing 1. A fan 5 is provided adjacent the housing rear wall to take air from the air-conditioned room into the housing through the air suction holes 2 and blow out air having been heat exchanged in the internal heat exchanger 4 through an air blow-out opening 3 provided in the bottom of the housing adjacent the front wall thereof. The internal heat exchanger 4 has a coolant flow line 9, which is branched into a first branch line 9a extending upward from the side of a substantially central inlet of the internal heat exchanger 4 and a second branch line 9b extending downward. On their outlet side, the two branch lines 9a and 9b are joined together by a coupler 9c provided outside the internal heat exchanger 4. An on-off valve 10 is provided on the second branch 9b and closed when a predetermined temperature is approached by the temperature of the air-conditioned room.
In this system, when the temperature of the room becomes the neighborhood of a predetermined temperature during a cooling operation, the on-off valve 10 is turned off, and coolant is allowed to flow through the first branch Line 9a. Thus, the cooling air is reduced to one half for gently reducing the temperature in the air-conditioned room. In this operation, drain water produced as a result of condensation in an upper part of the internal heat exchanger 4, falls as drops and is gasified by air passing through a lower part of the internal heat exchanger 4. Therefore, the drying of the room is prevented.
As shown, by the closing of the on-off valve 10 on the second branch line 10 in the neighborhood of the predetermined temperature, a substantial drying effect can no longer be expected due to the gasification of drain in a lower part of the internal heat exchanger 4, although the cooling air output is reduced to one half. For this reason, the on-off valve is opened when drying the room. Therefore, this prior art system still has the problem of excessive reduction of the temperature of the air-conditioned room.
The invention seeks to solve the above problems inherent in the prior art air conditioner. Specifically, it is a first object of the invention to provide an air conditioner, which permits drying of a room without substantially reducing the temperature thereof, i.e., without causing any chillness to be felt, and can improve the comfortability of the room.
A second object of the invention is to provide a method of controlling an air conditioner, which can realize a gentle cooling mode in which the air-conditioned room is dried while holding the temperature thereof in the neighborhood of a predetermined temperature, and also a gentle drying mode in which the room is dried while substantially holding the prevailing temperature.